The present invention relates in general to electromechanical circuit design, and more particularly to a flexible radio frequency identification tag for mail efficiency measurement applications.
Traditional circuit board assemblies use rigid insulated materials to form a substrate for the mounting of electronic components. According to well known prior art designs, the signal flow between electronic components is effected by wire connections (e.g., copper traces) printed on the substrate. The electronic components themselves are connected to these wire traces via solder. The rigidity of the substrate material prevents cracking of the copper solder joint connections and insures the integrity of these connections when the device is subjected to mechanical stress.
Certain specialized applications require circuit board assemblies of size greater than approximately 4 cm2 to be flexible. One such application is mail efficiency processing measurement wherein the circuit board assemblies are disposed within or on envelopes which pass through mail sorting equipment. The circuit board assemblies in such an application may be designed to incorporate low frequency antennae and associated electronic circuitry. The circuit board assembly must be designed to withstand the stresses of being passed through mechanical sorting machines.
According to the present invention, a radio frequency identification tag is provided having a printed RF coil integrated with a flexible substrate, and an integrated circuit area of the substrate adjacent the coil, wherein the integrated circuit area is reinforced to protect electrical components thereon. The radio frequency tag of the present invention is designed to endure mechanical stresses far in excess of the stresses which standard circuit board assemblies are normally subjected to. The tag of the present invention is also designed to be sufficiently thin and light for use in mail processing measurement applications.
The integrated antenna and circuit area are disposed on the same substrate thereby resulting in increased reliability and decreased complexity over prior art designs having antenna elements separate from the sensing circuit.
According to another aspect of the present invention is a method of making an identification tag, the method comprising providing a flexible substrate having an antenna portion and an integrated circuit portion; forming an antenna on the antenna portion of the substrate; forming a sensing circuit on a laminate substrate and securing the laminate substrate to the integrated circuit portion of the flexible substrate; forming a connection between the sensing circuit and the antenna on the substrate; and encapsulating the sensing circuit to form a semi-rigid area on the substrate while the antenna portion remains flexible.